The concept of tens and hundreds in students with down síndrome.

Abstract

We present an evaluation of the understanding that adolescents and adults with Down syndrome (DS) have of the decimal number system. The results of two studies are presented. The first was a case study with interviews of three adolescents and three adults with Down syndrome. Our results indicate that their conceptual understanding of the meaning of the tens and hundreds places is not as well developed as their ability to read, write and work with numbers of up to three digits. We also analyse the progress made by a 17- year-old student with Down syndrome after following a learning programme intended to improve her understanding of the tens place. To this end, we designed number tasks using four constructs: counting, grouping, partitioning and ordering. The student’s achievements in the counting construct were greater than in the others, exhibiting an understanding and use of the tens as a unit of counting to solve many of the number tasks proposed. Also evident was a progression in her understanding of the positional value. We observed differences in her success rate and variability in her responses depending on the method used in the tasks to represent the numbers.